The present invention generally relates to systems for loading and/or unloading fluids for ships, commonly referred to as marine loading systems. These systems are used to transfer a fluid product between a ship and a quay or between two ships.
Fluid product is understood to mean a liquid or gaseous product.
More particularly, the present invention concerns the devices for controlling movement, positioning and connection of such loading and/or unloading systems.
Generally, marine loading systems have a fluid transfer line end that is fixed to a base and connected to a tank of fluid to be transferred, and an opposite line end that is moveable and provided with a coupling adapted for connecting to a target duct, itself connected to a fluid tank.
Two families of fluid loading systems for ships are known, which are distinguished by their structure: systems for transfer by rigid pipes and systems for transfer by flexible pipes.
In the family of systems for transfer by rigid pipes, loading arm systems and pantograph systems can be distinguished.
The loading arm is an articulated tubing arrangement, comprising a base, connected to fluid tank, on which there is mounted a first pipe, designated inner pipe, via a portion of tube with a 90° bend enabling rotation of one of its ends about a vertical axis, and the other end about a horizontal axis. At the opposite end of the inner tube, a second pipe, designated outer pipe, is rotatably mounted about a horizontal axis. A coupling is mounted at the end of the outer pipe. Each of the three rotations is controlled by a jack or hydraulic motor.
The pantograph systems, like the loading arms, comprise a base connected to a tank. A crane is rotatably mounted on that base. The crane comprises a boom carrying a pipe for the fluid. At the end of the boom there is mounted a pantograph composed of articulated pipes for the fluid, and enabling a coupling to be moved that is mounted at the free end of the pantograph. The inclination of the pantograph is controlled by a rotation at the end of the boom. The movement of the pantograph is controlled by hydraulic motors and by a jack for the rotation on the base.
Lastly, the flexible piping systems generally comprise a line in which is conveyed the fluid product and a mechanical system enabling the line to be maneuvered. There are several types of maneuvering systems, but in all cases they include a manipulating crane or structure which supports the coupling for connecting the flexible piping.
In general, the loading system comprises an actuator at its end enabling the coupling to be clamped or unclamped. In general, this is one or more jacks or one or more hydraulic motors.
In practice, in most systems, the coupling is articulated at its end with three degrees of rotational freedom. In this way an angular orientation of the plane of the coupling relative to the plane of the target duct is possible independently of the inclination of the arm, the plane of the coupling remains parallel to the plane of the target duct on approach for the connection, and then, once the coupling has been clamped onto the target duct, these articulations enable a “floating” movement of the assembly. In practice, the rotations are controlled by the operator via hydraulic motors or jacks until connection has of the coupling to the target duct been achieved. Once the coupling has been clamped the hydraulic motors or jacks are disengaged or “set to freewheel” to enable the loading system to follow the movements of the target duct without constraining the coupling.
The two families of loading devices described above have structural differences, but their control systems are designed according to the same general principle of operation. It is noted that, in all cases, the coupling has at least three degrees of freedom relative to the base bearing the fixed end of the duct, and that the movements in each of these degrees of freedom are independently controlled by actuators. The operator has a command interface enabling him to control the movement of the coupling.
Each actuator is controlled either separately by an independent control of on/off type, or by a simultaneous proportional control.
In the case of on/off independent controls, the operator can act independently on each of the controls to control a particular member of the loading system. The combined action on the group of actuators enables the coupling to be positioned at a desired point in space.
In the case of proportional controls, the operator has a command input interface comprising a proportional control cooperating with a calculator such that acting on said proportional control with higher or lower magnitude leads to at least one proportional control instruction that is respectively of higher or lower magnitude for the corresponding actuators, resulting in a movement of the coupling at a speed of movement that is respectively higher or lower
The operator may thus directly control the movement of the coupling, and may thus in particular achieve movement of the coupling that is rectilinear, and/or at constant speed, since the calculator composes the movement of the coupling by acting on all the actuators simultaneously.
In general, the actuators used are hydraulic, for example a hydraulic motor or jack, but the use of electric actuators is also known, for example electric motors, or pneumatic actuators. The actuators equipping marine loading systems are controlled either by on/off control, with a constant speed of movement, and in certain cases, with the possibility of setting two speeds of movement at will for the independent controls of on/off type, or by proportional distributors, in the case of proportional controls.
In all cases, the connection of the coupling to the target duct is made manually, the operator thus maneuvers the loading system, with or without the intermediary of a control calculator in order to come to connect the coupling on the target duct.
These control devices are difficult to implement, in that the operator must know the functioning and kinematics of the marine loading system perfectly Furthermore, he must compensate for the movements of the ship, in particular in the case of rough sea. This increases the risk of the coupling striking against obstacles or against the target duct, which may damage the seals of the coupling. The maneuvering and the connection thus require qualified personnel.
A system is known making it possible to facilitate the connection of a coupling to a target duct in which the coupling is linked in advance by a cable to the target duct. A cable is thrown between the quay or the ship bearing the base and the ship bearing the target duct, then attached by operators between the target duct and the base. A winch then enables the arm to be advanced along the tensioned cable and thus the coupling to be drawn towards the target duct. This system is commonly called a “targeting system”. It is a semi-automatic system: once the cable has been connected, an operator must control the movement of the coupling along the cable by actuating the winding operation. A guiding cone is provided for the final phase of the approach. Once the coupling has been brought near, an operator must finalize its connection and its closure manually.
This mode of semi-automatic connection requires experienced staff and a suitable heavy mechanical structure (in particular a motor adapted to draw the arm along the cable, an anchorage point for the opposite end of the cable, and a guiding cone for the approach in the final phase).
On the basis of these observations, the invention aims to provide a device for facilitating the operation of controlling movement of the coupling for the operator, in particular to make it possible to succeed in connecting the coupling in unfavorable sea conditions, and more generally to facilitate the connection and make it more rapid in all cases, while reducing the risk of striking of the coupling.